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mariadb/row/row0vers.c
inaam e0ce800fa7 branches/zip issue# 33 
This fix makes two basic changes in blob handling:
(The bug was introduced in r2252)

1) The blob prefixes are no longer stored in the undo if
  a) We are modifying a delete marked record and
  b) The record was delete marked by an already committed trx.

2) When building old row version to check if one of these versions
can hold an implicit lock on the record we stop our probe if
  a) The version is delete marked and
  b) The delete marking is done by a trx which is different from
     the current active trx on the record.

Reviewed by: Heikki
2008-07-29 17:06:18 +00:00

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/******************************************************
Row versions
(c) 1997 Innobase Oy
Created 2/6/1997 Heikki Tuuri
*******************************************************/
#include "row0vers.h"
#ifdef UNIV_NONINL
#include "row0vers.ic"
#endif
#include "dict0dict.h"
#include "dict0boot.h"
#include "btr0btr.h"
#include "mach0data.h"
#include "trx0rseg.h"
#include "trx0trx.h"
#include "trx0roll.h"
#include "trx0undo.h"
#include "trx0purge.h"
#include "trx0rec.h"
#include "que0que.h"
#include "row0row.h"
#include "row0upd.h"
#include "rem0cmp.h"
#include "read0read.h"
#include "lock0lock.h"
/*********************************************************************
Finds out if an active transaction has inserted or modified a secondary
index record. NOTE: the kernel mutex is temporarily released in this
function! */
UNIV_INTERN
trx_t*
row_vers_impl_x_locked_off_kernel(
/*==============================*/
/* out: NULL if committed, else the active
transaction; NOTE that the kernel mutex is
temporarily released! */
const rec_t* rec, /* in: record in a secondary index */
dict_index_t* index, /* in: the secondary index */
const ulint* offsets)/* in: rec_get_offsets(rec, index) */
{
dict_index_t* clust_index;
rec_t* clust_rec;
ulint* clust_offsets;
rec_t* version;
rec_t* prev_version;
dulint trx_id;
dulint prev_trx_id;
mem_heap_t* heap;
mem_heap_t* heap2;
dtuple_t* row;
dtuple_t* entry = NULL; /* assignment to eliminate compiler
warning */
trx_t* trx;
ulint vers_del;
ulint rec_del;
ulint err;
mtr_t mtr;
ulint comp;
ut_ad(mutex_own(&kernel_mutex));
#ifdef UNIV_SYNC_DEBUG
ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));
#endif /* UNIV_SYNC_DEBUG */
mutex_exit(&kernel_mutex);
mtr_start(&mtr);
/* Search for the clustered index record: this is a time-consuming
operation: therefore we release the kernel mutex; also, the release
is required by the latching order convention. The latch on the
clustered index locks the top of the stack of versions. We also
reserve purge_latch to lock the bottom of the version stack. */
clust_rec = row_get_clust_rec(BTR_SEARCH_LEAF, rec, index,
&clust_index, &mtr);
if (!clust_rec) {
/* In a rare case it is possible that no clust rec is found
for a secondary index record: if in row0umod.c
row_undo_mod_remove_clust_low() we have already removed the
clust rec, while purge is still cleaning and removing
secondary index records associated with earlier versions of
the clustered index record. In that case there cannot be
any implicit lock on the secondary index record, because
an active transaction which has modified the secondary index
record has also modified the clustered index record. And in
a rollback we always undo the modifications to secondary index
records before the clustered index record. */
mutex_enter(&kernel_mutex);
mtr_commit(&mtr);
return(NULL);
}
heap = mem_heap_create(1024);
clust_offsets = rec_get_offsets(clust_rec, clust_index, NULL,
ULINT_UNDEFINED, &heap);
trx_id = row_get_rec_trx_id(clust_rec, clust_index, clust_offsets);
mtr_s_lock(&(purge_sys->latch), &mtr);
mutex_enter(&kernel_mutex);
trx = NULL;
if (!trx_is_active(trx_id)) {
/* The transaction that modified or inserted clust_rec is no
longer active: no implicit lock on rec */
goto exit_func;
}
if (!lock_check_trx_id_sanity(trx_id, clust_rec, clust_index,
clust_offsets, TRUE)) {
/* Corruption noticed: try to avoid a crash by returning */
goto exit_func;
}
comp = page_rec_is_comp(rec);
ut_ad(index->table == clust_index->table);
ut_ad(!!comp == dict_table_is_comp(index->table));
ut_ad(!comp == !page_rec_is_comp(clust_rec));
/* We look up if some earlier version, which was modified by the trx_id
transaction, of the clustered index record would require rec to be in
a different state (delete marked or unmarked, or have different field
values, or not existing). If there is such a version, then rec was
modified by the trx_id transaction, and it has an implicit x-lock on
rec. Note that if clust_rec itself would require rec to be in a
different state, then the trx_id transaction has not yet had time to
modify rec, and does not necessarily have an implicit x-lock on rec. */
rec_del = rec_get_deleted_flag(rec, comp);
trx = NULL;
version = clust_rec;
for (;;) {
mutex_exit(&kernel_mutex);
/* While we retrieve an earlier version of clust_rec, we
release the kernel mutex, because it may take time to access
the disk. After the release, we have to check if the trx_id
transaction is still active. We keep the semaphore in mtr on
the clust_rec page, so that no other transaction can update
it and get an implicit x-lock on rec. */
heap2 = heap;
heap = mem_heap_create(1024);
err = trx_undo_prev_version_build(clust_rec, &mtr, version,
clust_index, clust_offsets,
heap, &prev_version);
mem_heap_free(heap2); /* free version and clust_offsets */
if (prev_version) {
row_ext_t* ext;
clust_offsets = rec_get_offsets(
prev_version, clust_index, NULL,
ULINT_UNDEFINED, &heap);
vers_del = rec_get_deleted_flag(prev_version,
comp);
prev_trx_id = row_get_rec_trx_id(prev_version,
clust_index,
clust_offsets);
/* If the trx_id and prev_trx_id are
different and if the prev_version is marked
deleted then the prev_trx_id must have
already committed for the trx_id to be able to
modify the row. Therefore, prev_trx_id cannot
hold any implicit lock. */
if (0 != ut_dulint_cmp(trx_id, prev_trx_id)
&& vers_del) {
mutex_enter(&kernel_mutex);
break;
}
/* The stack of versions is locked by mtr.
Thus, it is safe to fetch the prefixes for
externally stored columns. */
row = row_build(ROW_COPY_POINTERS, clust_index,
prev_version, clust_offsets,
NULL, &ext, heap);
entry = row_build_index_entry(row, ext, index, heap);
/* entry may be NULL if a record was inserted
in place of a deleted record, and the BLOB
pointers of the new record were not
initialized yet. But in that case,
prev_version should be NULL. */
ut_a(entry);
}
mutex_enter(&kernel_mutex);
if (!trx_is_active(trx_id)) {
/* Transaction no longer active: no implicit x-lock */
break;
}
/* If the transaction is still active, the previous version
of clust_rec must be accessible if not a fresh insert; we
may assert the following: */
ut_ad(err == DB_SUCCESS);
if (prev_version == NULL) {
/* It was a freshly inserted version: there is an
implicit x-lock on rec */
trx = trx_get_on_id(trx_id);
break;
}
/* If we get here, we know that the trx_id transaction is
still active and it has modified prev_version. Let us check
if prev_version would require rec to be in a different
state. */
/* We check if entry and rec are identified in the alphabetical
ordering */
if (0 == cmp_dtuple_rec(entry, rec, offsets)) {
/* The delete marks of rec and prev_version should be
equal for rec to be in the state required by
prev_version */
if (rec_del != vers_del) {
trx = trx_get_on_id(trx_id);
break;
}
/* It is possible that the row was updated so that the
secondary index record remained the same in
alphabetical ordering, but the field values changed
still. For example, 'abc' -> 'ABC'. Check also that. */
dtuple_set_types_binary(entry,
dtuple_get_n_fields(entry));
if (0 != cmp_dtuple_rec(entry, rec, offsets)) {
trx = trx_get_on_id(trx_id);
break;
}
} else if (!rec_del) {
/* The delete mark should be set in rec for it to be
in the state required by prev_version */
trx = trx_get_on_id(trx_id);
break;
}
if (0 != ut_dulint_cmp(trx_id, prev_trx_id)) {
/* The versions modified by the trx_id transaction end
to prev_version: no implicit x-lock */
break;
}
version = prev_version;
}/* for (;;) */
exit_func:
mtr_commit(&mtr);
mem_heap_free(heap);
return(trx);
}
/*********************************************************************
Finds out if we must preserve a delete marked earlier version of a clustered
index record, because it is >= the purge view. */
UNIV_INTERN
ibool
row_vers_must_preserve_del_marked(
/*==============================*/
/* out: TRUE if earlier version should be preserved */
dulint trx_id, /* in: transaction id in the version */
mtr_t* mtr) /* in: mtr holding the latch on the clustered index
record; it will also hold the latch on purge_view */
{
#ifdef UNIV_SYNC_DEBUG
ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));
#endif /* UNIV_SYNC_DEBUG */
mtr_s_lock(&(purge_sys->latch), mtr);
if (trx_purge_update_undo_must_exist(trx_id)) {
/* A purge operation is not yet allowed to remove this
delete marked record */
return(TRUE);
}
return(FALSE);
}
/*********************************************************************
Finds out if a version of the record, where the version >= the current
purge view, should have ientry as its secondary index entry. We check
if there is any not delete marked version of the record where the trx
id >= purge view, and the secondary index entry and ientry are identified in
the alphabetical ordering; exactly in this case we return TRUE. */
UNIV_INTERN
ibool
row_vers_old_has_index_entry(
/*=========================*/
/* out: TRUE if earlier version should have */
ibool also_curr,/* in: TRUE if also rec is included in the
versions to search; otherwise only versions
prior to it are searched */
const rec_t* rec, /* in: record in the clustered index; the
caller must have a latch on the page */
mtr_t* mtr, /* in: mtr holding the latch on rec; it will
also hold the latch on purge_view */
dict_index_t* index, /* in: the secondary index */
const dtuple_t* ientry) /* in: the secondary index entry */
{
const rec_t* version;
rec_t* prev_version;
dict_index_t* clust_index;
ulint* clust_offsets;
mem_heap_t* heap;
mem_heap_t* heap2;
const dtuple_t* row;
const dtuple_t* entry;
ulint err;
ulint comp;
ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX)
|| mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX));
#ifdef UNIV_SYNC_DEBUG
ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));
#endif /* UNIV_SYNC_DEBUG */
mtr_s_lock(&(purge_sys->latch), mtr);
clust_index = dict_table_get_first_index(index->table);
comp = page_rec_is_comp(rec);
ut_ad(!dict_table_is_comp(index->table) == !comp);
heap = mem_heap_create(1024);
clust_offsets = rec_get_offsets(rec, clust_index, NULL,
ULINT_UNDEFINED, &heap);
if (also_curr && !rec_get_deleted_flag(rec, comp)) {
row_ext_t* ext;
/* The stack of versions is locked by mtr.
Thus, it is safe to fetch the prefixes for
externally stored columns. */
row = row_build(ROW_COPY_POINTERS, clust_index,
rec, clust_offsets, NULL, &ext, heap);
entry = row_build_index_entry(row, ext, index, heap);
/* If entry == NULL, the record contains unset BLOB
pointers. This must be a freshly inserted record. If
this is called from
row_purge_remove_sec_if_poss_low(), the thread will
hold latches on the clustered index and the secondary
index. Because the insert works in three steps:
(1) insert the record to clustered index
(2) store the BLOBs and update BLOB pointers
(3) insert records to secondary indexes
the purge thread can safely ignore freshly inserted
records and delete the secondary index record. The
thread that inserted the new record will be inserting
the secondary index records. */
/* NOTE that we cannot do the comparison as binary
fields because the row is maybe being modified so that
the clustered index record has already been updated to
a different binary value in a char field, but the
collation identifies the old and new value anyway! */
if (entry && !dtuple_coll_cmp(ientry, entry)) {
mem_heap_free(heap);
return(TRUE);
}
}
version = rec;
for (;;) {
heap2 = heap;
heap = mem_heap_create(1024);
err = trx_undo_prev_version_build(rec, mtr, version,
clust_index, clust_offsets,
heap, &prev_version);
mem_heap_free(heap2); /* free version and clust_offsets */
if (err != DB_SUCCESS || !prev_version) {
/* Versions end here */
mem_heap_free(heap);
return(FALSE);
}
clust_offsets = rec_get_offsets(prev_version, clust_index,
NULL, ULINT_UNDEFINED, &heap);
if (!rec_get_deleted_flag(prev_version, comp)) {
row_ext_t* ext;
/* The stack of versions is locked by mtr.
Thus, it is safe to fetch the prefixes for
externally stored columns. */
row = row_build(ROW_COPY_POINTERS, clust_index,
prev_version, clust_offsets,
NULL, &ext, heap);
entry = row_build_index_entry(row, ext, index, heap);
/* If entry == NULL, the record contains unset
BLOB pointers. This must be a freshly
inserted record that we can safely ignore.
For the justification, see the comments after
the previous row_build_index_entry() call. */
/* NOTE that we cannot do the comparison as binary
fields because maybe the secondary index record has
already been updated to a different binary value in
a char field, but the collation identifies the old
and new value anyway! */
if (entry && !dtuple_coll_cmp(ientry, entry)) {
mem_heap_free(heap);
return(TRUE);
}
}
version = prev_version;
}
}
/*********************************************************************
Constructs the version of a clustered index record which a consistent
read should see. We assume that the trx id stored in rec is such that
the consistent read should not see rec in its present version. */
UNIV_INTERN
ulint
row_vers_build_for_consistent_read(
/*===============================*/
/* out: DB_SUCCESS or DB_MISSING_HISTORY */
const rec_t* rec, /* in: record in a clustered index; the
caller must have a latch on the page; this
latch locks the top of the stack of versions
of this records */
mtr_t* mtr, /* in: mtr holding the latch on rec */
dict_index_t* index, /* in: the clustered index */
ulint** offsets,/* in/out: offsets returned by
rec_get_offsets(rec, index) */
read_view_t* view, /* in: the consistent read view */
mem_heap_t** offset_heap,/* in/out: memory heap from which
the offsets are allocated */
mem_heap_t* in_heap,/* in: memory heap from which the memory for
*old_vers is allocated; memory for possible
intermediate versions is allocated and freed
locally within the function */
rec_t** old_vers)/* out, own: old version, or NULL if the
record does not exist in the view, that is,
it was freshly inserted afterwards */
{
const rec_t* version;
rec_t* prev_version;
dulint trx_id;
mem_heap_t* heap = NULL;
byte* buf;
ulint err;
ut_ad(dict_index_is_clust(index));
ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX)
|| mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX));
#ifdef UNIV_SYNC_DEBUG
ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));
#endif /* UNIV_SYNC_DEBUG */
ut_ad(rec_offs_validate(rec, index, *offsets));
trx_id = row_get_rec_trx_id(rec, index, *offsets);
ut_ad(!read_view_sees_trx_id(view, trx_id));
rw_lock_s_lock(&(purge_sys->latch));
version = rec;
for (;;) {
mem_heap_t* heap2 = heap;
trx_undo_rec_t* undo_rec;
dulint roll_ptr;
dulint undo_no;
heap = mem_heap_create(1024);
/* If we have high-granularity consistent read view and
creating transaction of the view is the same as trx_id in
the record we see this record only in the case when
undo_no of the record is < undo_no in the view. */
if (view->type == VIEW_HIGH_GRANULARITY
&& ut_dulint_cmp(view->creator_trx_id, trx_id) == 0) {
roll_ptr = row_get_rec_roll_ptr(version, index,
*offsets);
undo_rec = trx_undo_get_undo_rec_low(roll_ptr, heap);
undo_no = trx_undo_rec_get_undo_no(undo_rec);
mem_heap_empty(heap);
if (ut_dulint_cmp(view->undo_no, undo_no) > 0) {
/* The view already sees this version: we can
copy it to in_heap and return */
buf = mem_heap_alloc(in_heap,
rec_offs_size(*offsets));
*old_vers = rec_copy(buf, version, *offsets);
rec_offs_make_valid(*old_vers, index,
*offsets);
err = DB_SUCCESS;
break;
}
}
err = trx_undo_prev_version_build(rec, mtr, version, index,
*offsets, heap,
&prev_version);
if (heap2) {
mem_heap_free(heap2); /* free version */
}
if (err != DB_SUCCESS) {
break;
}
if (prev_version == NULL) {
/* It was a freshly inserted version */
*old_vers = NULL;
err = DB_SUCCESS;
break;
}
*offsets = rec_get_offsets(prev_version, index, *offsets,
ULINT_UNDEFINED, offset_heap);
trx_id = row_get_rec_trx_id(prev_version, index, *offsets);
if (read_view_sees_trx_id(view, trx_id)) {
/* The view already sees this version: we can copy
it to in_heap and return */
buf = mem_heap_alloc(in_heap, rec_offs_size(*offsets));
*old_vers = rec_copy(buf, prev_version, *offsets);
rec_offs_make_valid(*old_vers, index, *offsets);
err = DB_SUCCESS;
break;
}
version = prev_version;
}/* for (;;) */
mem_heap_free(heap);
rw_lock_s_unlock(&(purge_sys->latch));
return(err);
}
/*********************************************************************
Constructs the last committed version of a clustered index record,
which should be seen by a semi-consistent read. */
UNIV_INTERN
ulint
row_vers_build_for_semi_consistent_read(
/*====================================*/
/* out: DB_SUCCESS or DB_MISSING_HISTORY */
const rec_t* rec, /* in: record in a clustered index; the
caller must have a latch on the page; this
latch locks the top of the stack of versions
of this records */
mtr_t* mtr, /* in: mtr holding the latch on rec */
dict_index_t* index, /* in: the clustered index */
ulint** offsets,/* in/out: offsets returned by
rec_get_offsets(rec, index) */
mem_heap_t** offset_heap,/* in/out: memory heap from which
the offsets are allocated */
mem_heap_t* in_heap,/* in: memory heap from which the memory for
*old_vers is allocated; memory for possible
intermediate versions is allocated and freed
locally within the function */
const rec_t** old_vers)/* out: rec, old version, or NULL if the
record does not exist in the view, that is,
it was freshly inserted afterwards */
{
const rec_t* version;
mem_heap_t* heap = NULL;
byte* buf;
ulint err;
dulint rec_trx_id = ut_dulint_zero;
ut_ad(dict_index_is_clust(index));
ut_ad(mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_X_FIX)
|| mtr_memo_contains_page(mtr, rec, MTR_MEMO_PAGE_S_FIX));
#ifdef UNIV_SYNC_DEBUG
ut_ad(!rw_lock_own(&(purge_sys->latch), RW_LOCK_SHARED));
#endif /* UNIV_SYNC_DEBUG */
ut_ad(rec_offs_validate(rec, index, *offsets));
rw_lock_s_lock(&(purge_sys->latch));
/* The S-latch on purge_sys prevents the purge view from
changing. Thus, if we have an uncommitted transaction at
this point, then purge cannot remove its undo log even if
the transaction could commit now. */
version = rec;
for (;;) {
trx_t* version_trx;
mem_heap_t* heap2;
rec_t* prev_version;
dulint version_trx_id;
version_trx_id = row_get_rec_trx_id(version, index, *offsets);
if (rec == version) {
rec_trx_id = version_trx_id;
}
mutex_enter(&kernel_mutex);
version_trx = trx_get_on_id(version_trx_id);
mutex_exit(&kernel_mutex);
if (!version_trx
|| version_trx->conc_state == TRX_NOT_STARTED
|| version_trx->conc_state == TRX_COMMITTED_IN_MEMORY) {
/* We found a version that belongs to a
committed transaction: return it. */
if (rec == version) {
*old_vers = rec;
err = DB_SUCCESS;
break;
}
/* We assume that a rolled-back transaction stays in
TRX_ACTIVE state until all the changes have been
rolled back and the transaction is removed from
the global list of transactions. */
if (!ut_dulint_cmp(rec_trx_id, version_trx_id)) {
/* The transaction was committed while
we searched for earlier versions.
Return the current version as a
semi-consistent read. */
version = rec;
*offsets = rec_get_offsets(version,
index, *offsets,
ULINT_UNDEFINED,
offset_heap);
}
buf = mem_heap_alloc(in_heap, rec_offs_size(*offsets));
*old_vers = rec_copy(buf, version, *offsets);
rec_offs_make_valid(*old_vers, index, *offsets);
err = DB_SUCCESS;
break;
}
heap2 = heap;
heap = mem_heap_create(1024);
err = trx_undo_prev_version_build(rec, mtr, version, index,
*offsets, heap,
&prev_version);
if (heap2) {
mem_heap_free(heap2); /* free version */
}
if (UNIV_UNLIKELY(err != DB_SUCCESS)) {
break;
}
if (prev_version == NULL) {
/* It was a freshly inserted version */
*old_vers = NULL;
err = DB_SUCCESS;
break;
}
version = prev_version;
*offsets = rec_get_offsets(version, index, *offsets,
ULINT_UNDEFINED, offset_heap);
}/* for (;;) */
if (heap) {
mem_heap_free(heap);
}
rw_lock_s_unlock(&(purge_sys->latch));
return(err);
}
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